1. Field of the Invention
The present invention relates to an ultrasonic color Doppler diagnostic apparatus which performs image interpolation so as to improve the ultrasonic frame rate in appearance. In recent years, the importance of obtaining a grasp or understanding of the state of blood behavior in the heart and the carotid arteries has been rising or increasing in the field of clinical diagnosis. The present invention here is an ultrasonic color Doppler diagnostic apparatus which can display color images of the state of blood behavior safely and simply in real time.
2. Description of the Related Arts
Conventional ultrasonic color Doppler diagnostic apparatuses display in real time a combination of the B mode (Brightness) image of the muscle of the heart or other organ in the specimen or subject under examinations and the average speed, speed dispersion, or Doppler signal power of the blood flowing through a specimen (hereinafter referred to as blood flow speed data). These convectional apparatuses enabled observation of the flow of blood in body organs and was extremely convenient in obtaining a grasp of the state of the blood behavior in the organs.
As described in more detail later with reference to the drawings, ideally, it is desired to see the blood flow changing slowly and smoothly with each television frame. However, there is the problem that the image changes in spurts, and the doctor using the conventional apparatuses or considered the movement of the heart and changes in the state of the blood flow as awkward or confusing and therefore could not make a sufficient or reliable diagnosis. The following three methods were considered in the prior art to overcome this problem: First, as the first conventional method, the control of the beam former was changed so as to reduce the number of ultrasonic pulses and received in the same direction of the specimen. This change in control was accomplished by changing the direction of sending and receiving signals in rough angles, or in the alternative, the range of angles of signal transmission and reception was made narrower so as to substantially improve the ultrasonic frame rate. In this first method, however, the flow rate data obtained could only be obtained at rough positions in two dimensions, or for the alternative method the flow rate data could only be obtained in a narrow range of angles. As a result, there was an undeniable a deterioration of the quality of the flow image as compared with the usual display.
As a second conventional method, simultaneous multidirectional signal transmission and reception was used so as to obtain signals received from a plurality of directions. In this second conventional method, at least a plurality of beam formers were necessary, so inevitably the cost was higher and the apparatus was larger in size, which was not necessarily satisfactory to the user. In addition, cost reductions made possible by advances in semiconductor technology further cannot be expected to contribute much in terms of the cost or size of beam formers.
As a third conventional method, an interpolation and a weighting are employed to obtain an estimated image between two original images.
In this third conventional method, it is possible to improve the apparent ultrasonic frame rate simply and inexpensively. However, when the position and angle of the blood flow differ greatly among the original images, then, a false blood flow completely different from the true images ends up being displayed and there is the danger of mistaken diagnosis.